1. Field of the Invention
The present invention relates to an auxiliary power drive for chain driven systems, and more particularly, to a roller sprocket auxiliary drive for a pedal cycle.
2. Description of the Related Art
The increasing popularity of pedal cycles for older citizens for exercise and environmentally friendly transportation encourages the consideration of some type of power assist for a pedal cycle. Ideally, this power assist should function in conjunction with the pedal power of the cycle and should utilize the existing gearing systems of the chain drive. The power assist device should be simple to attach to,and remove from a wide number of pedal cycle configurations. Moreover, the power assist device should be lightweight, rugged and simple to operate.
Many known power assist devices are bolt-on types primarily utilizing gasoline motor packages. These devices frequently employ a friction drive bearing on the crown or sidewalls of the cycle tire. Higher efficiency mechanical drives, such as bolt on electrical drives have also been proposed.
U.S. Pat. No. 5,242,028 discloses a motorized bicycle drive system which drives the bicycle independent of the pedal drive, employing a separate drive chain. Such a device is complex and difficult to install.
Thus, there is a need for an auxiliary drive attachment which uses the existing chain drive for power delivery.
An object of the present invention is to provide a power drive attachment which bears directly on the existing chain drive of a pedal cycle and is simple to install.
Another object of the present invention is to provide a drive sprocket incorporating a free wheel hub which permits pedal power without drive motor rotation, even though the power drive unit remains engaged with the chain or chain ring.
A further object of the present invention is that the existing pedal cycle rear sprocket gear ratios can also be utilized by the power drive attachment.
Still another object of the present invention is the mounting system which is combined with a roller drive sprocket hub, which enables quick attachment and also accommodates irregularities in the alignment between the sprocket and the cycle chain ring.
By incorporating either a worm reduction gear or a bevel reduction gear in the drive, the combined advantages of orientation of the drive motor axis of rotation along the cycle frame and the ability to use a high speed drive motor are achieved in a single compact package attachable to the cycle frame and between the pedal arms or alongside the rear fork.
The present invention introduces a compact drive motor mounted adjacent the chain ring of a pedal cycle, such that the power assist drive can apply tension to the associated drive chain, and can supplement or replace pedal power through the combination of drive components.
In accomplishing these and other objectives of the present invention, in one embodiment, there is provided a power drive attachment for a pedal cycle. The cycle includes a frame, a pair of pedals, a drive chain and a chain ring mounted on the frame. The power drive attachment includes a drive motor mounted on the frame of the cycle. An output drive sprocket is mounted on the motor in close vicinity to the chain ring, wherein the drive chain is captured between the drive sprocket and the chain ring. Means pivotally mount the drive motor and sprocket on the cycle frame for increasing the tension on the drive chain and for accommodating irregularities in the alignment between the drive sprocket and the drive chain.
In a second embodiment, a power drive attachment includes a drive motor mounted on the frame of the cycle. An output drive sprocket is mounted on the motor for engaging an unoccupied portion of the chain ring. The drive sprocket includes roller tooth means for engaging a section of the chain ring or rear sprocket which is not communicating with the drive chain, to drive the cycle.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.